Cover assembly of secondary battery and secondary battery

ABSTRACT

A cover assembly includes a cover plate including a gas vent, a gas exhaust valve configured to seal the gas vent and deform in response to an increase in temperature to get out of a state of sealing the gas vent, and a sealing part. The gas exhaust valve includes a metal sheet and a fixing part. The metal sheet seals the gas vent. The sealing part is arranged between the metal sheet and the cover plate for sealing a gap between the metal sheet and the cover plate. The fixing part is connected to the metal sheet. The metal sheet is fixed to the cover plate by the fixing part. The fixing part is configured to deform in response to an increase in temperature in such a manner that the metal sheet gets out of the state of sealing the gas vent.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of application Ser. No.16/941,419, filed on Jul. 28, 2020, which claims priority to ChinesePatent Application No. 201910726079.9, filed on Aug. 7, 2019, thecontents of both of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present disclosure relates to the technical field of energy storagedevices, and in particular, to a cover assembly of a secondary batteryand a secondary battery.

BACKGROUND

As an important part of a new energy vehicle, a secondary battery isimportant in its safety performance. With charging and discharging ofthe secondary battery, gas will be generated inside the secondarybattery. If the gas has a high pressure, the secondary battery mayexplode. Accordingly, a gas pressure-controlled vent may be provided ona cover plate of the secondary battery.

Since one secondary battery has small capacity or small power, aplurality of secondary batteries is usually provided to form a batterymodule for use. Once one secondary battery of the battery moduleexperiences thermal runaway, heat generated thereby will be quicklytransferred to other secondary batteries of the battery module.Accordingly, the other secondary batteries also experience thermalrunaway, thereby causing sharp rise in temperature and gas pressure.When the existing gas pressure-controlled vent experiences thermalrunaway, there is a risk that the secondary battery will explode ifthere is no enough time to release the pressure.

Therefore, it is needed to design a new secondary battery to solve theabove problems, so as to improve the safety performance of the secondarybattery.

SUMMARY

The present disclosure provides a cover assembly of a secondary batteryand a secondary battery that can solve the problem in the related artand improve a safety performance of the secondary battery.

In a first aspect, the present disclosure provides a cover assembly of asecondary battery, including:

a cover plate including a gas vent;

a gas exhaust valve configured to seal the gas vent and deform inresponse to an increase in temperature to get out of a state of sealingthe gas vent;

a sealing part arranged between the gas exhaust valve and the coverplate and surrounding the gas vent for sealing a gap between the gasexhaust valve and the cover plate.

In a possible design, the gas exhaust valve includes a metal sheet and afixing part, and the metal sheet seals the gas vent;

the sealing part is arranged between the metal sheet and the cover platefor sealing a gap between the metal sheet and the cover plate;

the fixing part is connected to the metal sheet, and the metal sheet isfixed to the cover plate by the fixing part; and

the fixing part is configured to deform in response to an increase intemperature in such a manner that the metal sheet gets out of the stateof sealing the gas vent.

In a possible design, the fixing part has a melting point within a rangeof 80° C. to 200° C.

In a possible design, the fixing part includes a main body portion and aconnection portion;

the main body portion is connected to a side surface of the metal sheetfacing away from the sealing part; and

along a length direction of the cover assembly, the connection portionis connected to two sides of the main body portion, and the connectionportion is connected to the metal sheet.

In a possible design, the connection portion has a ring structure andsurrounds a side wall of the metal sheet.

In a possible design, one of the connection portion and the metal sheetis provided with a protrusion, and the other one of the connectionportion and the metal sheet is provided with a first groove; and

the protrusion matches the first groove.

In a possible design, the main body portion is provided with a firstcenter hole; and

the first center hole is opposite to the gas vent.

In a possible design, along a thickness direction of the cover assembly,a projection of the fixing part at least partially overlaps a projectionof the sealing part.

In a possible design, the cover assembly further includes a pressingblock, and the pressing block is fixed to the cover plate;

the pressing block includes a second center hole, and the second centerhole is opposite to the gas vent; and

the pressing block presses against a side surface of the fixing partfacing away from the sealing part, and the fixing part is fixed to thecover plate by the pressing block.

In a possible design, along a thickness direction of the cover assembly,a projection of the pressing block does not overlap a projection of themetal sheet.

In a possible design, the cover plate is provided with a second groove,and the sealing part is at least partially received in the secondgroove.

In a second aspect, the present disclosure provides a secondary battery,including:

a case including an opening;

an electrode assembly received in the case, the electrode assemblyincluding: a first electrode plate, a second electrode plate, and aseparator arranged between the first electrode plate and the secondelectrode plate; and

the cover assembly described above, the cover assembly covering theopening of the case.

A technical solution provided by the present disclosure can achieve thefollowing beneficial effects.

For the cover assembly of the secondary battery and the secondarybattery provided by the present disclosure, the gas exhaust valve sealsthe gas vent, and the gas exhaust valve deforms in response to anincrease in temperature to get out of a state of sealing the gas vent.When temperature inside the case of the secondary battery rises, gasinside the case can be exhausted via the gas vent, thereby reducing arisk of thermal runaway of the secondary battery, and also slowing downthe thermal runaway of the secondary battery and thus providingpassengers with sufficient escape time. Since the sealing part isarranged between the gas exhaust valve and the cover plate and surroundsthe gas vent for sealing a gap between the gas exhaust valve and thecover plate, sealing of the gas exhaust valve is improved. This canprevent electrolyte leakage of the secondary battery under a normaloperation condition or prevent external water vapor from entering aninterior of the case, which would otherwise reduce the safetyperformance and service life of the secondary battery.

It should be understood that the foregoing general description and thefollowing detailed description are merely exemplary and are not intendedto limit the present disclosure.

DESCRIPTION OF DRAWINGS

In order to more clearly illustrate technical solutions in embodimentsof the present disclosure or in the related art, the accompanyingdrawings used in the embodiments and in the related art are brieflyintroduced as follows. It should be noted that the drawings described asfollows are merely part of the embodiments of the present disclosure,other drawings can also be acquired by those skilled in the art withoutpaying creative efforts.

FIG. 1 is a schematic diagram of a structure of a secondary batteryaccording to an embodiment of the present disclosure;

FIG. 2 is a front cross-sectional view illustrating a structure of asecondary battery according to an embodiment of the present disclosure;

FIG. 3 is an exploded view of a structure of a cover assembly of asecondary battery according to an embodiment of the present disclosure;

FIG. 4 is a front view of a cover assembly of a secondary batteryaccording to an embodiment of the present disclosure;

FIG. 5 is a cross-sectional view taken along line A-A of FIG. 4 ;

FIG. 6 is an enlarged view of an area B of FIG. 5 ;

FIG. 7 is a partial view of a structure of a cover plate shown in FIG. 6;

FIG. 8 is an exploded view of a structure of a cover assembly of asecondary battery according to another embodiment of the presentdisclosure;

FIG. 9 is a front view of a cover assembly of a secondary batteryaccording to another embodiment of the present disclosure;

FIG. 10 is a cross-sectional view taken along line C-C of FIG. 9 ;

FIG. 11 is an enlarged view of an area D of FIG. 10 ;

FIG. 12 is a schematic view of a structure of a gas exhaust valve shownin FIG. 11 ;

FIG. 13 is an exploded view of a structure of a cover assembly of asecondary battery according to still another embodiment of the presentdisclosure;

FIG. 14 is a front view of a cover assembly of a secondary batteryaccording to still another embodiment of the present disclosure;

FIG. 15 is a cross-sectional view taken along line E-E of FIG. 14 ;

FIG. 16 is an enlarged view of an area F of FIG. 15 ;

FIG. 17 is a schematic view of a structure of a gas exhaust valve shownin FIG. 16 ;

FIG. 18 is an exploded view of a structure of a cover assembly of asecondary battery according to yet another embodiment of the presentdisclosure;

FIG. 19 is a front view of a cover assembly of a secondary batteryaccording to yet another embodiment of the present disclosure;

FIG. 20 is a cross-sectional view taken along line G-G of FIG. 19 ;

FIG. 21 is an enlarged view of an area H of FIG. 20 ;

FIG. 22 is a schematic view of a structure of a gas exhaust valve shownin FIG. 21 ;

FIG. 23 is a schematic view of a structure of a fixing part shown inFIG. 22 ; and

FIG. 24 is a schematic view of a structure of a metal sheet shown inFIG. 22 .

Reference Signs:

-   100—secondary battery;-   1—cover assembly;-   11—cover plate;-   111—anti-explosion vent;-   112—gas vent;-   113—first recess;-   114—second recess;-   115—second groove;-   12—anti-explosion plate;-   13—gas exhaust valve;-   131—metal sheet;-   131 a—protrusion;-   132—fixing part;-   132 a—main body portion;-   132 b—connection portion;-   132 c—first groove;-   132 d—first center hole;-   14—sealing part;-   15—pressing block ;-   151—second center hole;-   16—insulation plate;-   17—electrode terminal;-   2—case;-   3—electrode assembly;-   4—connection plate.

The drawings herein are incorporated into and constitute a part of thepresent specification, illustrate embodiments of the present disclosureand explain principles of the present disclosure together with thespecification.

DESCRIPTION OF EMBODIMENTS

The technical solutions in the embodiments of the present disclosure aredescribed in the following with reference to the accompanying drawings.It should be noted that, the described embodiments are merely exemplaryembodiments of the present disclosure, which shall not be interpreted asproviding limitations to the present disclosure. All other embodimentsobtained by those skilled in the art without creative efforts accordingto the embodiments of the present disclosure are within the scope of thepresent disclosure.

The terms used in the embodiments of the present disclosure are merelyfor the purpose of describing particular embodiments but not intended tolimit the present disclosure. Unless otherwise noted in the context, thesingular form expressions “a”, “an”, “the” and “said” used in theembodiments and appended claims of the present disclosure are alsointended to represent plural form expressions thereof.

It should be understood that the term “and/or” used herein is merely anassociation relationship describing associated objects, indicating thatthere may be three relationships, for example, A and/or B may indicatethat three cases, i.e., A existing individually, A and B existingsimultaneously, B existing individually. In addition, the character “/”herein generally indicates that the related objects before and after thecharacter form an “or” relationship.

It should be understood that, the terms such as “upper”, “lower”,“left”, “right” and the like are used to indicate positions shown in thedrawing, instead of being construed as limitations of the embodiment ofthe present disclosure. In addition, when an element is described asbeing “on” or “under” another element in the context, it should beunderstood that the element can be directly or via an intermediateelement located “on” or “under” another element.

FIG. 1 is a schematic diagram of a structure of a secondary batteryaccording to an embodiment of the present disclosure. FIG. 2 is a frontcross-sectional view illustrating a structure of a secondary batteryaccording to an embodiment of the present disclosure. As shown in FIG. 1and FIG. 2 , an embodiment of the present disclosure provides asecondary battery 100. The secondary battery 100 includes a case 2, anelectrode assembly 3 and a cover assembly 1.

The case 2 may be in a hexahedron shape or other shape. A receivingcavity is formed inside the case 2 for receiving the electrode assembly3 and an electrolyte. The case 2 is open at its one end, so that theelectrode assembly 3 can be placed in the receiving cavity of the case 2through this opening. A plurality of electrode assemblies 3 may bearranged in the receiving cavity, and the plurality of electrodeassemblies 3 is stacked with respect to each other. The case 2 mayinclude a metal material such as aluminum or aluminum alloy, and mayfurther include an insulation material such as plastic.

The electrode assembly 3 includes an electrode unit and tab. Theelectrode unit includes a negative electrode, a positive electrode, anda separator. The separator is located between a negative electrode and apositive electrode that are adjacent, so as to separate the negativeelectrode from the positive electrode.

In one embodiment, the negative electrode, the separator, and thepositive electrode are sequentially stacked and wound to form theelectrode unit of the electrode assembly 3. That is, the electrode unithas a wound structure. In another embodiment, the negative electrode,the separator, and the positive electrode are sequentially stacked toform the electrode unit of the electrode assembly 3, and this electrodeunit has a stacked structure. At the same time, the electrode unitincludes a slit after being formed, and the electrolyte can enter theelectrode unit via the slit to infiltrate the negative electrode and thepositive electrode.

The negative electrode includes a negative current collector (forexample, a copper foil) and a negative active material layer (forexample, carbon or silicon) coated on a surface of the negative currentcollector. The positive electrode includes a positive current collector(for example, an aluminum foil) and a positive active material layer(for example, a ternary material, lithium iron phosphate or lithiumcobaltate) coated on a surface of the positive current collector. Anegative electrode tab is connected to the negative electrode andprotrudes from the electrode unit. The negative electrode tab may beformed by directly cutting the negative current collector. A positiveelectrode tab is connected to the positive electrode and protrudes fromthe electrode unit. The positive electrode tab may be formed by directlycutting the positive current collector.

FIG. 3 is an exploded view of a structure of a cover assembly of asecondary battery according to an embodiment of the present disclosure.As shown in FIG. 1 to FIG. 3 , the cover assembly 1 includes a coverplate 11 and electrode terminals 17. The cover plate 11 is fixed to theopening of the case 2, thereby making the electrode assembly 3 and theelectrolyte be enclosed in the receiving cavity of the case 2. Theelectrode terminals 17 are arranged at the cover plate 11 and include anegative electrode terminal and a positive electrode terminal. The twoelectrode terminals 17 are electrically connected to respective tabs viaconnection plates 4. The cover plate 11 is provided with ananti-explosion vent 111, and the anti-explosion plate 12 covers theanti-explosion vent 111.

Specifically, for the secondary battery 100 in which the tabs protrudefrom a top of the electrode unit, the above-mentioned connection plates4 are located between the electrode unit of the electrode assembly 3 andthe cover plate 11. The connection plates 4 include a negativeconnection plate and a positive connection plate. The negativeconnection plate is configured to connect the negative electrode tabwith the negative electrode terminal, and the positive connection plateis configured to connect the positive electrode with the positiveelectrode terminal. The cover assembly 1 further includes an insulationplate 16 that insulates the cover plate 11 from the electrode assembly3.

The plurality of secondary batteries 100 described above can form abattery module. In the battery module, if one secondary batteryexperiences thermal runaway, the generated heat will be transferred toan adjacent secondary battery, thereby accelerating thermal runaway ofthe nearby secondary battery.

In order to solve this problem, an embodiment of the present disclosureprovides a cover assembly 1 of a secondary battery. FIG. 4 is a frontview of a cover assembly of a secondary battery according to anembodiment of the present disclosure. FIG. 5 is a cross-sectional viewtaken along line AA of FIG. 4 . FIG. 6 is an enlarged view of an area Bof FIG. 5 . As shown in FIG. 3 to FIG. 6 , the cover assembly 1 includesa cover plate 11, a gas exhaust valve 13, and a sealing part 14.

The cover plate 11 includes a gas vent 112. The gas exhaust valve 13seals the gas vent 112, and the gas exhaust valve 13 deforms in responseto an increase in temperature in such a manner that the gas exhaustvalve 13 no longer seals the gas vent 112. A sealing part 14 is arrangedbetween the gas exhaust valve 13 and the cover plate 11 and surroundsthe gas vent 112, so as to seal a gap between the gas exhaust valve 13and the cover plate 11.

In this embodiment, the cover assembly 1 seals the gas vent 112 by thegas exhaust valve 13, and the gas exhaust valve 13 deforms in responseto an increase in temperature in such a manner that the gas exhaustvalve 13 no longer seals the gas vent 112. When temperature inside thecase 2 of the secondary battery 100 rises, the gas exhaust valve 13 nolonger seals the gas vent 112, so that the gas inside the case 2 can beexhausted via the gas vent 112. In this way, on the one hand, thepressure inside the case 2 can be reduced so as to prevent explosion ofthe secondary battery 100, and on the other hand, partial heat can betaken away by exhausting gas so as to slow down the thermal runaway ofthe secondary battery 100 and provide sufficient escape time forpassengers.

Since the sealing part 14 is arranged between the gas exhaust valve 13and the cover plate 11 and surrounds the gas vent 112 so that thesealing part 14 seals the gap between the gas exhaust valve 13 and thecover plate 11, sealing of the gas exhaust valve 13 is improved. Thiscan prevent electrolyte leakage of the secondary battery 100 under orprevent external water vapor from entering an interior of the case 2 anormal operation condition, which would otherwise reduce the safetyperformance and service life of the secondary battery 100.

In an implementation, the gas exhaust valve 13 has a lower melting pointthan the cover plate 11. For example, the gas exhaust valve 13 may beformed by a material of PP (polypropylene), PE (polyethylene) or thelike. When the temperature inside the case 2 exceeds the melting pointof the gas exhaust valve 13, the gas exhaust valve 13 will deform, thatis, melting or softening occurs. At this time, the gas exhaust valve 13will get out of a state of sealing the gas vent 112, so that the gasvent 112 is open and thus the gas inside the case 2 of the secondarybattery 100 can be exhausted to an exterior of the case 2 via the gasvent 112.

In an implementation, the cover assembly 1 may further include apressing block 15. Along a thickness direction Z of the cover assembly,the pressing block 15 presses against the gas exhaust valve 13. Thepressing block 15 may be welded to the cover plate 11, so that the gasexhaust valve 13 is fixed to the cover plate 11.

FIG. 7 is a partial view of a structure of a cover plate shown in FIG. 6. In an implementation, the cover plate 11 includes a first recess 113and a second recess 114. With reference to FIG. 6 and FIG. 7 , along thethickness direction Z of the cover assembly 1, the first recess 113 islocated above the gas vent 112 and the second recess 114 is locatedabove the first recess 113. An inner diameter of the first recess 113 islarger than a diameter of the gas vent 112, and an inner diameter of thesecond recess 114 is larger than the inner diameter of the first recess113. The gas exhaust valve 13 is received in the first recess 113, andthe pressing block 15 is received in the second recess 114.

With the first recess 113 and the second recess 114, a top surface ofthe pressing block 15 is substantially aligned with a top surface of thecover plate 11, so that the pressing block 15 and the gas exhaust valve13 do not occupy too much space, thereby increasing an energy density ofthe secondary battery.

In an implementation, the cover plate 11 is provided with a secondgroove 115, and the sealing part 14 is received in the second groove115. When the cover plate 11 is provided with the second groove 115 andthe sealing part 14 is at least partially received in the second groove115, the sealing part 14 is in contact with a bottom of the secondgroove 115 and the gas exhaust valve 13. In this way, the sealing of thegas exhaust valve 13 is improved. Moreover, with the second groove 115,a space occupied by the cover assembly 1 in the thickness direction Zcan be reduced, thereby increasing the energy density of the secondarybattery 100.

In an implementation, the second groove 115 is located at an uppersurface of the cover plate 11 at a circumference of the gas vent 112,and a lower surface of the gas exhaust valve 13 matches the sealing part14 in the second groove 115. Specifically, the second groove 115 may beformed at a bottom surface of the first recess 113, and the secondgroove 115 may also be formed at other position of the cover plate 11.

In an implementation, the second groove 115 is located at a lowersurface of the cover plate 11 at the circumference of the gas vent 112,and an upper surface of the gas exhaust valve 13 matches the sealingpart 14 in the second groove 115.

In an implementation, the second groove 115 is located at a pore wall atthe circumference of the gas vent 112, and a circumferential outersurface of the gas exhaust valve 13 matches the sealing part 14 in thesecond groove 115.

Another exemplary embodiment will be described in the following, inwhich the elements that are the same as those in the above exemplaryembodiments will not be further described herein, and only dissimilarelements will be described in detail.

FIG. 8 is an exploded view of a structure of a cover assembly of asecondary battery according to another embodiment of the presentdisclosure. FIG. 9 is a front view of a cover assembly of a secondarybattery according to another embodiment of the present disclosure. FIG.10 is a cross-sectional view taken along line C-C of FIG. 9 . FIG. 11 isan enlarged view of an area D of FIG. 10 . FIG. 12 is a schematic viewof a structure of a gas exhaust valve shown in FIG. 11 .

As shown in FIG. 8 to FIG. 12 , in a possible implementation manner, thegas exhaust valve 13 includes a metal sheet 131 and a fixing part 132,and the metal sheet 131 seals the gas vent 112. The sealing part 14 isarranged between the metal sheet 131 and the cover plate 11 for sealinga gap between the metal sheet 131 and the cover plate 11. The fixingpart 132 is connected to the metal sheet 131, and the metal sheet 131 isfixed to the cover plate 11 by the fixing part 132. The fixing part 132deforms in response to an increase in temperature, so as to make themetal sheet 131 get out of a state of sealing the gas vent 112.

In an implementation, the metal sheet may be an aluminum sheet, astainless steel sheet or a nickel sheet, preferably an aluminum sheet,which has advantages of light weight and good penetration resistance.

The fixing part 132 has a lower melting point than the cover plate 11.For example, the fixing part 132 may be made of PP (polypropylene), PE(polyethylene) or the like. When the temperature inside the case 2exceeds the melting point of the fixing part 132, the fixing part 132will deform, that is, melting or softening occurs. At this time, themetal sheet 131 moves with the deformation of the fixing part 132,thereby getting out of a state of sealing the gas vent 112. In thiscase, the gas vent 112 is open, and the gas inside the case 2 of thesecondary battery 100 can be exhausted to an exterior via the gas vent112. Illustratively, the melting point of the fixing part 132 may bewithin a range of 80° C. to 200° C.

The sealing part 14 may be an annular sealing ring, and the annularsealing ring is arranged between the metal sheet 131 and the cover plate11 and is in contact with the metal sheet 131 and the cover plate 11,thereby ensuring the sealing between the metal sheet 131 and the gasvent 112.

The above-described gas exhaust valve 13 includes a metal sheet 131.Since the metal sheet 131 has a better penetration resistance, it canprevent the electrolyte in the case 2 of the secondary battery 100 frompenetrating to the exterior of the case 2, and also prevent moisture orother gas outside the case 2 from penetrating into the case 2, therebyreducing the service life of the secondary battery 100. With the fixingpart 132, rigidity of the entire gas exhaust valve 13 can be increased,so that the gas exhaust valve 13 does not undergo a big deformation whenpressure is applied to the sealing part 14.

In an implementation, as shown in FIG. 11 and FIG. 12 , the fixing part132 includes a main body portion 132 a and a connection portion 132 b.The main body portion 132 a is connected to a side surface of the metalsheet 131 facing away from the sealing part 14. Along a length directionX of the cover assembly 1, the connection portion 132 b is connected totwo sides of the main body portion 132 a, and the connection portion 132b is connected to the metal sheet 131.

The metal sheet 131 is connected to the cover plate 11 via theabove-described connection portion 132 b. Specifically, the main bodyportion 132 a, the connection portion 132 b, and the metal sheet 131 maybe formed by injection molding. With the connection portion 132 b,reliability of a connection between the metal sheet 131 and the coverplate 11 is improved, and the above-described pressing block 15 canpress against the main body portion 132 a.

In an implementation, the connection portion 132 b has a ring structureand surrounds a side wall of the metal sheet 131. With the connectionportion 132 b having a ring structure and surrounding the side wall ofthe metal sheet 131, strength of a connection between the fixing part132 and the metal sheet 131 can be further increased, and the fixingpart 132 can more uniformly and comprehensively sense a temperaturechange inside the case 2. Once the temperature inside the case 2 isextremely high, the connection portion 132 b will melt and deform,thereby causing the metal sheet 131 to get out of a state of sealing thegas vent 112.

In an implementation, the main body portion 132 a is provided with afirst center hole 132 d, and the first center hole 132 d is opposite tothe gas vent 112. When the temperature inside the case 2 of thesecondary battery 100 rises to a preset value (a threshold value setbased on a temperature at which thermal runaway occurs), the connectionportion 132 b melts or deforms, and the metal sheet 131 accordinglymoves or deforms. The first center hole 132 d is opposite to the gasvent 112, that is, a center of the first center hole 132 d substantiallycorresponds to a center of the metal sheet 131. In this way, the bindingof the fixing part 132 to the metal sheet 131 is reduced, therebyreducing hindrance to movement or deformation of the metal sheet 131.

Another exemplary embodiment will be described in the following, inwhich the elements that are the same as those in the above exemplaryembodiments will not be further described herein, and only dissimilarelements will be described in detail.

FIG. 13 is an exploded view of a structure of a cover assembly of asecondary battery according to still another embodiment of the presentdisclosure. FIG. 14 is a front view of a cover assembly of a secondarybattery according to still another embodiment of the present disclosure.FIG. 15 is a cross-sectional view taken along line E-E of FIG. 14 . FIG.16 is an enlarged view of an area F of FIG. 15 . FIG. 17 is a schematicview of a structure of a gas exhaust valve shown in FIG. 16 ,

As shown in FIG. 13 to FIG. 17 , in an implementation, the main bodyportion 132 a may not be provided with the first center hole 132 d, butmay be integrally connected to a side of the metal sheet 131 facing awayfrom the sealing part 14.

In an implementation, along the thickness direction Z of the coverassembly 1, a projection of the fixing part 132 at least partiallyoverlaps a projection of the sealing part 14. As described above, withthe fixing part 132, an overall rigidity of the gas exhaust valve 13 isincreased. When the metal sheet 131 presses against the sealing part 14,if the fixing part 132 cannot at least partially cover the sealing part14, the metal sheet 131 will deform, thereby affecting a sealing effectthereof. Thus, the projection of the setting fixing part 132 at leastpartially overlaps the projection of the sealing part 14, so that theoverall rigidity of the gas exhaust valve 13 is increased and thepressure on the sealing part 14 is increased, thereby ensuring thesealing of the secondary battery 100.

In an implementation, along the thickness direction Z of the coverassembly 1, the projection of the sealing part 14 is totally within theprojection of the fixing part 132.

In an implementation, the cover assembly 1 further includes a pressingblock 15, and the pressing block 15 is fixed to the cover plate 11. Thepressing block 15 includes a second center hole 151, and the secondcenter hole 151 is opposite to the gas vent 112. The pressing block 15presses against a side surface of the fixing part 132 facing away fromthe sealing part 14, and the fixing part 132 is fixed to the cover plate11 by the pressing block 15.

The pressing block 15 presses against the fixing part 132 of the gasexhaust valve 13, and the pressing block 15 may be welded to the coverplate 11, so that the gas exhaust valve 13 is fixed to the gas vent 112.

When the secondary battery 100 is about to experience thermal runaway,if the pressing block 15 applies an excessive pressure onto the metalsheet 131, deformation of the metal sheet 131 will be affected, therebyresulting in untimely gas exhaust. With the second center hole 151, thepressing block 15 does not apply an excessive pressure onto the metalsheet 131.

In an implementation, along the thickness direction Z of the coverassembly 1, a projection of the pressing block 15 does not overlap a theprojection of the metal sheet 131. In other words, along the thicknessdirection Z of the cover assembly 1, the projection of the metal sheet131 does not totally fall within the second center hole 151 describedabove. When the secondary battery is about to experience thermalrunaway, a temperature of the gas inside the case 2 will cause thefixing part 132 to melt or deform, and the metal sheet 131 is separatedfrom the gas vent 112. Under an impact of the gas, the metal sheet 131leaves the cover assembly 1 of the secondary battery 100 via the secondcenter hole 151. With the projection of the pressing block 15 notoverlapping the projection of the metal sheet 131, after the fixing part132 melts or deforms, the pressing block 15 does not block the metalsheet 131, so that the metal sheet 131 falls to the exterior of the case2 of the secondary battery instead of falling to the interior of thecase 2 of the secondary battery 100. This ensures the safety performanceof the secondary battery 100.

Another exemplary embodiment will be described in the following, inwhich the elements that are the same as those in the above exemplaryembodiments will not be further described herein, and only dissimilarelements will be described in detail.

FIG. 18 is an exploded view of a structure of a cover assembly of asecondary battery according to yet another embodiment of the presentdisclosure. FIG. 19 is a front view of a cover assembly of a secondarybattery according to yet another embodiment of the present disclosure.FIG. 20 is a cross-sectional view taken along line G-G of FIG. 19 . FIG.21 is an enlarged view of an area H of FIG. 20 . FIG. 22 is a schematicview of a structure of a gas exhaust valve shown in FIG. 21 . FIG. 23 isa schematic view of a structure of a fixing part shown in FIG. 22 . FIG.24 is a schematic view of a structure of a metal sheet shown in FIG. 22.

As shown in FIG. 18 to FIG. 24 , in an implementation, one of theconnection portion 132 b and the metal sheet 131 is provided with aprotrusion 131 a, and the other one of the connection portion 132 b andthe metal sheet 131 is provided with a first groove 132 c. Theprotrusion 131 a matches the first groove 132 c. In this embodiment, themetal sheet 131 is provided with the protrusion 131 a, and theconnection portion 132 b is provided with the first groove 132 c. Withthe first groove 132 c matching the protrusion 131 a, strength of aconnection between the metal sheet 131 and the connection portion 132 bcan be further improved. Moreover, with the first groove 132 c, both atop surface and a bottom surface of the protrusion 131 a of the metalsheet 131 are covered by the connection portion 132 b. In this case,when the secondary battery 100 is not in thermal runaway, the metalsheet 131 does not deform easily.

In the embodiment shown in FIG. 18 to FIG. 24 , along the thicknessdirection Z of the cover assembly 1, the projection of the pressingblock 15 does not overlap the projection of the metal sheet 131. Afterthe fixing part 132 melts or deforms, the pressing block 15 does notblock the metal sheet 131, so that the metal sheet 131 drops to theexterior of the case 2 of the secondary battery instead of falling tothe interior of the case 2 of the secondary battery 100. This can ensurethe safety performance of the secondary battery 100.

An embodiment of the present disclosure further provides a secondarybattery 100, including the case 2, the electrode assembly 3, and thecover assembly 1 provided by any embodiment of the present disclosure.The case 2 includes an opening, and the electrode assembly 3 is receivedin the case 2. The electrode assembly 3 includes a first electrodeplate, a second electrode plate, and a separator arranged between thefirst electrode plate and the second electrode plat. The cover assembly1 covers the opening of the case 2, so as to make the electrode assembly3 be enclosed in the case 2.

In summary, for the cover assembly 1 of the secondary battery 100 andthe secondary battery provided by the embodiments of the presentdisclosure, when one secondary battery is in thermal runaway, with theincreasing of the temperature of the gas temperature inside the case 2,the gas vent 112 is opened by an adjacent secondary battery through thegas exhaust valve 13, thereby releasing gas pressure to reduce apossibility of explosion. This can also take away some heat, therebyslowing down the thermal runaway and providing the passengers withescape time.

The above-described embodiments are merely preferred embodiments of thepresent disclosure and are not intended to limit the present disclosure.Various changes and modifications can be made to the present disclosureby those skilled in the art. Any modifications, equivalent substitutionsand improvements made within the principle of the present disclosureshall fall into the protection scope of the present disclosure.

What is claimed is:
 1. A cover assembly of a secondary battery,comprising: a cover plate comprising a gas vent; a gas exhaust valveconfigured to seal the gas vent and deform in response to an increase intemperature to get out of a state of sealing the gas vent in such amanner that gas inside a case of the secondary battery is directlyexhausted to an exterior of the secondary battery via only the gas vent;and a sealing part arranged between the gas exhaust valve and the coverplate and surrounding the gas vent for sealing a gap between the gasexhaust valve and the cover plate; wherein: the gas exhaust valvecomprises a metal sheet and a fixing part, and the metal sheet seals thegas vent; the sealing part is arranged between the metal sheet and thecover plate for sealing a gap between the metal sheet and the coverplate; the fixing part is connected to the metal sheet, and the metalsheet is fixed to the cover plate by the fixing part; and the fixingpart is configured to deform in response to an increase in temperaturein such a manner that the metal sheet gets out of the state of sealingthe gas vent.
 2. The cover assembly according to claim 1, wherein thefixing part has a melting point within a range of 80° C. to 200° C. 3.The cover assembly according to claim 1, wherein: the fixing partcomprises a main body portion and a connection portion; the main bodyportion is connected to a surface of the metal sheet facing away fromthe sealing part; and along a length direction of the cover assembly,the connection portion is connected to two sides of the main bodyportion, and the connection portion is connected to the metal sheet. 4.The cover assembly according to claim 3, wherein the connection portionhas a ring structure and surrounds a side wall of the metal sheet. 5.The cover assembly according to claim 3, wherein: one of the connectionportion and the metal sheet is provided with a protrusion, and the otherone of the connection portion and the metal sheet is provided with afirst groove; and the protrusion matches the first groove.
 6. The coverassembly according to claim 3, wherein: the main body portion isprovided with a first center hole; and the first center hole is oppositeto the gas vent.
 7. The cover assembly according to claim 1, whereinalong a thickness direction of the cover assembly, a projection of thefixing part at least partially overlaps a projection of the sealingpart.
 8. The cover assembly according to claim 1, further comprising: apressing block fixed to the cover plate; wherein: the pressing blockcomprises a second center hole, and the second center hole is oppositeto the gas vent; and the pressing block presses against a surface of thefixing part facing away from the sealing part, and the fixing part isfixed to the cover plate by the pressing block.
 9. The cover assemblyaccording to claim 8, wherein an orthograph projection of the secondcenter hole on the cover plate overlaps with an orthographic projectionof the gas vent on the cover plate.
 10. The cover assembly according toclaim 8, wherein along a thickness direction of the cover assembly, aprojection of the pressing block does not overlap a projection of themetal sheet.
 11. The cover assembly according to claim 1, wherein thecover plate is provided with a second groove, and the sealing part is atleast partially received in the second groove.
 12. The cover assemblyaccording to claim 1, wherein the fixing part is in a shape of a plateand is integrally connected to a side of the metal sheet facing awayfrom the sealing part.
 13. The cover assembly according to claim 1,wherein an orthographic projection of the sealing part on the coverplate does not overlap with an orthographic projection of the gas venton the cover plate.
 14. A secondary battery, comprising: a casecomprising an opening; an electrode assembly received in the case,wherein the electrode assembly comprises a first electrode plate, asecond electrode plate, and a separator arranged between the firstelectrode plate and the second electrode plate; and a cover assemblycovering the opening of the case, wherein the cover assembly comprises:a cover plate comprising a gas vent; a gas exhaust valve configured toseal the gas vent and deform in response to an increase in temperatureto get out of a state of sealing the gas vent in such a manner that gasinside a case of the secondary battery is directly exhausted to anexterior of the secondary battery via only the gas vent; and a sealingpart arranged between the gas exhaust valve and the cover plate andsurrounding the gas vent for sealing a gap between the gas exhaust valveand the cover plate; wherein: the gas exhaust valve comprises a metalsheet and a fixing part, and the metal sheet seals the gas vent; thesealing part is arranged between the metal sheet and the cover plate forsealing a gap between the metal sheet and the cover plate; the fixingpart is connected to the metal sheet, and the metal sheet is fixed tothe cover plate by the fixing part; and the fixing part is configured todeform in response to an increase in temperature in such a manner thatthe metal sheet gets out of the state of sealing the gas vent.
 15. Thesecondary battery according to claim 14, wherein the fixing part has amelting point within a range of 80° C. to 200° C.
 16. The secondarybattery according to claim 14, wherein: the fixing part comprises a mainbody portion and a connection portion; the main body portion isconnected to a surface of the metal sheet facing away from the sealingpart; and along a length direction of the cover assembly, the connectionportion is connected to two sides of the main body portion, and theconnection portion is connected to the metal sheet.
 17. The secondarybattery according to claim 14, wherein along a thickness direction ofthe cover assembly, a projection of the fixing part at least partiallyoverlaps a projection of the sealing part.
 18. The secondary batteryaccording to claim 14, wherein the cover assembly further comprises: apressing block fixed to the cover plate; wherein: the pressing blockcomprises a second center hole, and the second center hole is oppositeto the gas vent; and the pressing block presses against a surface of thefixing part facing away from the sealing part, and the fixing part isfixed to the cover plate by the pressing block.
 19. The secondarybattery according to claim 14, wherein the cover plate is provided witha second groove, and the sealing part is at least partially received inthe second groove.
 20. The secondary battery according to claim 14,wherein the fixing part is in a shape of a plate and is integrallyconnected to a side of the metal sheet facing away from the sealingpart.